The recurring discussions regarding human flapping flight (if possible, by muscle-power!) have done more harm than good, because they distract attention from other more important subjects.

For example, the heed for the faster and larger flying creatures (such as large birds) and for high-speed aeroplanes to reduce speed when necessary, without corresponding loss of lift. All kinds of “ high lift devices ” have been invented for aeroplanes. All are based on the principle of making possible a steeper angle of attack or a higher wing-camber, thus giving greater lift without causing eddies that would lead to a break-away of the airflow on the upper surface.

The introduction of German “Stukas“ has been one of the great surprises of the present war. By means of this weapon, daring men, with the true fighting spirit, have already obtained innumerable successes of the greatest importance on all fronts. These results could not have been achieved but for the conviction that German scientists, and engineers had so perfected the design of this divebomber that it could withstand the exceptional demands made on it—especially on the engine and airscrew.

The high engine output necessary in order to effect further increases in flight speed must be transformed in the fullest possible measure by the airscrew into propulsive power. Three possibilities are open whereby the capacity of the airscrew for absorbing the engine power may be increased, namely, (1) by increasing the diameter, (2) by increasing the number and width of the blades, and (3) by increasing the peripheral speed. The increase in the diameter is limited by the effects of weight, the increase in the number and width of the blades by considerations of structure and design and the increase in the peripheral speed by the speed of sound. Of these limitations the last is of particular importance.

During the last twenty years a revival of interest in the subject of map projections has taken the form of a renewed attack upon certain basic limitations which face the cartographer. A necessary stimulus has been provided by the growth of a technique of air navigation, which in many ways has departed from the traditional practice of the marine navigator. From this and other directions emphasis has been laid on the need for precise cartographic representation of distance, direction and position on the earth. But although certain problems may be treated by devising new projections to meet special needs, it is obvious that there is a limit to any purely cartographic approach.

The requirements of the new navigation are, briefly, that its methods should be rapid, convenient to use, and of an accuracy consistent with the limitations imposed. The traditional solution by means of spherical trigonometry is thus ruled out on at least two of these counts. In its place, there are now available a number of graphical, mechanical and simplified tabular methods, many of which have no cartographic basis. Since a map projection is an obvious medium for the measurement of spherical relations, the needs of long-distance air navigation have encouraged the adaptation of certain projections in the form of special instruments and devices.

There is considerable lack of information regarding shear stresses in tapered beams. In this brief report these stresses are examined by a simple extension of the conventional engineering method for uniform beams, and where possible the results are compared with those of classical theory.

Complete agreement is obtained with the few existing classical solutions. The use of the engineering method is illustrated by its application to various types of beam, and curves are drawn illustrating the general nature of the influence of taper on shear stresses.

In a previous paper (Aircraft Engineering, November and December, 1938) the writer gave an account of proposed methods of calculating the stresses in tapered girders of a special type. The beam was assumed to have a web of constant thickness which could be dealt with as a two-dimensional stress system, while the booms were assumed to be concentrated lines of material having no flexural rigidity.

It was this latter assumption which appeared to represent one of the main limitations of the theory, so an attempt has been made to remove this limitation; a solution has been found, for the case of tapering booms at any rate, which puts the theory at least on the same level of rigour as the well known theory for parallel beams.

When J. A. Brinell, at the end of the last century, interested himself in the property hardness of metals, he could have had no idea of the importance to be attained later by the new line of investigation he was launching nor of the interesting machines and their applications for which his work was to provide the inspiration.

In the aircraft industry this form of test is not solely used to determine the property hardness as such, but is used to give some idea of the maximum tensile strength of the material. This use is illustrated by some of the specifications controlling the quality of aircraft material, in which hardness tests are required on a specified percentage of bars to ensure that the bars which are riot tensile tested will give a maximum tensile strength of not less than the minimum nor greater than the maximum specification values.

It is shown that weight can be saved, and stiffness gained by a proper choice of the design, that is the type of frame of any truss. A method is developed first to choose the best among several statically determinate designs. It is then demonstrated that, when a redundant truss has to carry one set of loads, it is always possible, by the removal of some bars, to get a statically determinate truss which is lighter, for the same ultimate stress. But the redundancy keeps its advantages when the structure has to carry several sets of loads in turn.